The invention relates to an installation for lifting sheets of glass, this operation consisting in guiding a sheet gripped in a substantially horizontal position to a substantially vertical position, where it is deposited, this in order to form stacks (stacking), or in guiding a sheet gripped in a substantially vertical position on a stack to a substantially horizontal position on a conveyor (unstacking).
In production units, the glass is obtained in the form of a web (by the "float glass" process, for example) which is then cut out into sheets.
The web and the sheets are conveyed by one (or more) horizontal principal conveyor(s).
These sheets are then lifted to a so-called gripping station in order to be stacked on handling trucks provided with panels (comprising a substantially horizontal plane and a substantially vertical plane) on which they come into abutment.
The glass web being directly cut out on the principal conveyor in the longitudinal direction (direction of the axis of the conveyor) and the transverse direction (direction perpendicular to the longitudinal direction in the plane of the conveyor), the delivery of objects increases and the lifting machines must operate (i.e. handle each sheet) at rapid rates (2 to 4 secs.) or very rapid rates (of the order of 2 secs.).
French Patent FR 86 05656 published under No. 2 597 453 describes a compact rapid elevator (lifting machine), in which rates of 2 to 4 secs. are obtained by multiplication of the number of gripping arms. In this way, in this elevator according to the prior art, there are two retractable gripping arms provided at each of their ends with gripping means (suction cups), which makes a total of four gripping points of which two are simultaneously active (one per arm).